Transport by the (Na+, K+) ATPase: Modulation by differentiation inducers and inhibition of protein synthesis in the MDCK kidney epithelial cell line
✍ Scribed by Brian G. Kennedy; Julia E. Lever
- Publisher
- John Wiley and Sons
- Year
- 1985
- Tongue
- English
- Weight
- 744 KB
- Volume
- 123
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
MDCK kidney epithelial cell cultures exposed to the differentiation inducer hexamethylene bisacetamide (HMBA) for 24 hours exhibited a 50% decrease in transport activity per (Na+, K+)-ATPase molecule (turnover number) but an unchanged number of pump sites (Kennedy and Lever, 1984). Inhibition of protein synthesis by either 10 pM cycloheximide or 2 pM emetine blocked the inhibitory effects of HMBA on N a + / K + pump efficiency assessed by measurements of [3H]-ouabain binding to intact cells, (Na+, K + ) ATPase activity of detergent-activated cell extracts, and ouabain-sensitive Rb+ uptake. In the absence of inducer treatment, inhibition of protein synthesis increased N a + / K + pump turnover number by twofold while maintaining Na+/K+ pump activity per cell at a constant level. lntracellular Na+ levels were decreased after cycloheximide treatment; therefore, pump stimulation was not due to substrate effects. Furthermore, cycloheximide effects of Rb+ uptake could be dissociated from effects on tight junctions. These observations suggest that t h e transport activity of the (Na+, K + ) ATPase is tightly regulated by factors dependent on protein synthesis.